In the semiconductor industry, it is common to use a scanning electron microscope (SEM) to observe the surface condition of a deposited wafer and transmission electron microscope (TEM) to examine the microstructure of a deposited wafer to ensure that finished microelectronic elements satisfy an expected standard. At first, a sample is cut from a wafer to be examined. After thoroughly polished, the sample becomes ultra-thin and is ready to be examined by an electron microscope for determining the quality of the wafer.
Conventional polishing tools for preparing an ultra-thin specimen are designed in accordance with the principle of three points deciding a plane. Nowadays, there are several companies manufacturing different kinds of polishing tools, such as South Bay Tech. and Allied Inc., etc. However, there exists several shortcomings in conventional polishing tools:
(a) conventional polishing tools are too heavy to be handled, mainly because there are made of copper or stainless steel, PA1 (b) conventional polishing tools have two Teflon-made footing pieces, which are difficult to be effectively positioned or have to utilize a micrometer during polishing a specimen. That brings about the increased cost and size of a conventional polishing tool. Further, a conventional polishing tool is usually made in such a way that the specimen to be polished is placed far away from Teflon-made footing pieces in order to secure a uniformity in thickness of the specimen. It results in an increase in the height of a polishing tool and thus is inconvenient for a user to place a conventional polishing tool on the stage of an optical microscope for primary examination. PA1 (c) It is common for any conventional polishing tool to use a holder to position a specimen. Since the holder used is immobile, it is unable to increase the accuracy of the specimen mounted on the holder. On the other hand, a cross section specimen for TEM observation is different from a plane view specimen for SEM observation. The prior design has to use different holders with varied shapes, instead of a single holder, for different types of specimens. Please refer to FIGS. 1 and 2 which are schematic diagrams showing a conventional L-shaped holder 11 and a conventional H-shaped holder 12, respectively.
FIG. 3 illustrates a polishing wheel 13 for polishing a specimen 14 stuck to an L-shaped holder 11. FIG. 4 illustrates a polishing wheel 13 for polishing a specimen 14 stuck to an H-shaped holder 12. A fine distance .DELTA. shown in FIG. 3 is measured with a micrometer (not shown). By using an optical microscope 15 shown in FIG. 5, a user may monitor the advanced cross-sectional line of the polished specimen 14. It can be seen from FIG. 5 that the length of the L-shaped holder 11 is limited by the distance between the lens and the stage of the optical microscope 15. However, a shorter L-shaped will lead to a difficulty in controlling the orientation of the specimen 14 relative to the top surface of the polishing wheel 13, results in a less accuracy of controlling the thickness of the specimen 14. FIG. 6 shows the H-shaped holder 12 placed on the stage of an optical microscope for examination.
Both AMER Co. and Precision TEM Inc. have developed polishing tools similar to the polishing tool 10 as shown in FIGS. 1 and 2. However, those polishing tools have a shortcoming of above-mentioned (c). Furthermore, the prior polishing tools with a steel-made stopper 17 which is used as a fixer for a rotary bolt 18 is subject to deformation and will hurt a user's fingers during polishing.
Thus, it is tried by the applicant to deal with the situation encountered with the prior art.